if (element == null || !isActuallyE(element)) {
      return 0;
    }
    Enum<?> e = (Enum<?>) element;
    return counts[e.ordinal()];
  }

  // Modification Operations
  @CanIgnoreReturnValue
  @Override
  public int add(E element, int occurrences) {
    checkIsE(element);
    checkNonnegative(occurrences, "occurrences");
    if (occurrences == 0) {

 * IteratorTester#newTargetIterator()} method. This is because it's impossible to test an Iterator
 * without changing its state, so the tester needs a steady supply of fresh Iterators.
 *
 * <p>If your iterator supports modification through {@code remove()}, you may wish to override the
 * verify() method, which is called after each sequence and is guaranteed to be called

 * IteratorTester#newTargetIterator()} method. This is because it's impossible to test an Iterator
 * without changing its state, so the tester needs a steady supply of fresh Iterators.
 *
 * <p>If your iterator supports modification through {@code remove()}, you may wish to override the
 * verify() method, which is called after each sequence and is guaranteed to be called

    if (element == null || !isActuallyE(element)) {
      return 0;
    }
    Enum<?> e = (Enum<?>) element;
    return counts[e.ordinal()];
  }

  // Modification Operations
  @CanIgnoreReturnValue
  @Override
  public int add(E element, int occurrences) {
    checkIsE(element);
    checkNonnegative(occurrences, "occurrences");
    if (occurrences == 0) {

 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface BiMap<K extends @Nullable Object, V extends @Nullable Object> extends Map<K, V> {
  // Modification Operations

  /**
   * {@inheritDoc}
   *
   * @throws IllegalArgumentException if the given value is already bound to a different key in this

  abstract ObjectCountHashMap<E> newBackingMap(int distinctElements);

  @Override
  public final int count(@CheckForNull Object element) {
    return backingMap.get(element);
  }

  // Optional Operations - Modification Operations

  /**
   * {@inheritDoc}
   *
   * @throws IllegalArgumentException if the call would result in more than {@link
   *     Integer#MAX_VALUE} occurrences of {@code element} in this multiset.
   */

  static final byte UNSET = 0;

  /** Number of bits used to store the numbers of hash table bits (max 30). */
  private static final int HASH_TABLE_BITS_MAX_BITS = 5;

  /** Use high bits of metadata for modification count. */
  static final int MODIFICATION_COUNT_INCREMENT = (1 << HASH_TABLE_BITS_MAX_BITS);

  /** Bitmask that selects the low bits of metadata to get hashTableBits. */

  public void testListIterator_unmodifiable() {
    runListIteratorTest(UNMODIFIABLE);
  }

  /*
   * For now, we don't cope with testing this when the list supports only some
   * modification operations.
   */
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @ListFeature.Require({SUPPORTS_SET, SUPPORTS_ADD_WITH_INDEX})
  public void testListIterator_fullyModifiable() {
    runListIteratorTest(MODIFIABLE);

  public void testListIterator_unmodifiable() {
    runListIteratorTest(UNMODIFIABLE);
  }

  /*
   * For now, we don't cope with testing this when the list supports only some
   * modification operations.
   */
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @ListFeature.Require({SUPPORTS_SET, SUPPORTS_ADD_WITH_INDEX})
  public void testListIterator_fullyModifiable() {
    runListIteratorTest(MODIFIABLE);

 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface BiMap<K extends @Nullable Object, V extends @Nullable Object> extends Map<K, V> {
  // Modification Operations

  /**
   * {@inheritDoc}
   *
   * @throws IllegalArgumentException if the given value is already bound to a different key in this